Most plural nouns are built by adding -s / -es to the singular.
cup – cups (pronounced as [s] after voiceless consonants)
wave – waves, toe – toes (pronounced as [z] after voiced consonants and vowels)
rose – roses (pronounced as [iz] after sibilants)
Special rules
1) -s, -sh, -ch, -x, -z, + -es.
loss – losses, bench – benches, bush – bushes, box – boxes, buzz -buzzes
2) – o + -es
buffalo – buffaloes, cargo – cargoes, echo – echoes, hero – heroes, potato – potatoes, motto – mottoes, mosquito – mosquitoes, volcano – volcanoes
But !
vowel + o + -s
cameo – cameos
cuckoo – cuckoos
folio – folios
radio – radios
+ other nouns (of foreign origin)
o+s
banjo, bravo, burro, canto, casino, chromo, contralto, dynamo, halo, junto, kilo, lasso, memento, photo, piano, proviso, quarto, solo, soprano, stiletto, torso, tyro, zero
3) consonant + y
y –> i + es
sky – skies
country – countries
But !
Vowel + y + -s
day – days
Note!
Most proper names ending in -y take the plural in -s.
Mary – Marys
Rowley – Rowleys
4) In some nouns ending in -f or -fe
-f→ -v + -es
beef – beeves
calf – calves
elf – elves
half – halves
knif – knives
leaf – leaves
life – lives
loaf – loaves
self – selves
sheaf – sheaves
shelf – shelves
thief – thieves
wife – wives
wolf – wolves
But !
The following nouns in -f or -fe take only -s
belief – beliefs
cliff – cliffs
cuff – cuffs
grief – griefs
gulf – gulfs
proof – proofs
safe – safes
Note!
Some nouns have both forms in the plural:
handkerchiefs/handkerchieves, hoofs/hooves, scarfs/scarves, wharfs/wharves
(I.P Krylova, E.M. Gordon, p.261)
5) Some nouns form their plural in -en.
ox – oxen
child – children
6) A few nouns form their plural by a change of vowel.
man – men (also firemen, salesmen etc.)
woman – women
foot – feet
tooth – teeth
goose – geese
mouse – mice
louse – lice
7) Some nouns have the same form in both singular and plural:
cod, deer, fish, grouse, sheep, heathen, salmon, swine, trout.
8) Some noun borrowed from from other languages have special plural forms.
– from Latin:
-um → -a
bacterium – bacteria
datum – data
stratum – strata
-us → – i
alumnus [ə’lʌmnəs]– alumni [ə’lʌmnaɪ]
radius – radii
stimulus – stimuli
terminus – termini
other Latin nouns:
apparatus – apparatus
index – indices
series – series
species – species
– from Greek:
-is → es
analysis – analyses
axis – axes
basis – bases
diagnosis – diagnoses
hypothesis – hypotheses
oasis – oases
synopsis – synopses
thesis – theses
-on → a
phenomenon – phenomena
criterion – criteria
! Some nouns have the new English plural along with the original foreign one:
appendix – appendices/appendixes
curriculum – curriculums/curricula,
formula – formulas/formulae,
memorandum – memorandums/memornda
(I.P. Krylova, E.M. Gordon, p. 262)
9) Plural compound nouns normally take -s in the last pat;
spoonful – spoonfuls
stepson – stepsons
forget-me-not – forget-me-nots
merry-go-round – merry-go-rounds
Sometimes -s is added to the first part.
editor-in-chief – editors-in-chief
maid-of-honor – maids-of-honor (‘the main bridesmaid at a wedding’)
son-in-law – sons-in-law
10) Nouns used only in the plural form (pluralia tantum)
– clothing (clothes, dungarees, jeans, pyjamas, shorts, trousers, trunks)
– tools/equipment (scissors, glasses/spectacles, scales, handcuffs, pliers)
– games (dominoes, darts, cards)
– other (contents, goods, remains, savings, stairs, thanks, troops, whereabouts)